An order-of-magnitude reduction of the nuclear magnetic moment of trivalent europium due to hyperfine-induced magnetic shielding was predicted by Elliott in 1957. With use of optical hole burning and optically detected nuclear quadrupole resonance in YAl${\mathrm{O}}_3$: ${\mathrm{Eu}}^{3+}$, this shielding has been measured for the first time. We find that the ground-state moment is reduced to 21% of its intrinsic value, while the moment in the excited ${}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}$ state is unaffected.

A molecular dynamics study on a system of infinitely thin hard rods is reported. At low densities, rotational and translational diffusion is adequately described by the Enskog theory, but at high densities (${\rho }^{*}\gg 1$) large deviations are observed. For ${\rho }^{*}\gg 1$, the rotational diffusion constant ($D_r$) and the longitudinal translational diffusion constant ($D_{\parallel }$) are compared with scaling predictions. The molecular dynamics results confirm that $D_r\sim {{\rho }^{*}}^{-2\mathrm{}}$, and are consistent with a predicted divergence of $D_{\parallel }\sim {{\rho }^{*}}^{\frac{1}{2}}$.

The inner product of two states in Hilbert space is interpreted in terms of a relationship between two or more distinct physical systems. This point of view suggests a generalized notion of measurement, within which the familiar types of measurement occur as special cases. A variety of novel measuring procedures are described, which relate overcomplete sets of states for a given system to complete sets for some larger system (of which the smaller system forms a part).

The $\mathrm{CP}$-nonconserving polarization of ${\mu }^{+}$ from $K_{\mu 3}$ decays in the direction (${\overrightarrow{\mathrm{p}}}_{\pi }\times {\overrightarrow{\mathrm{p}}}_{\mu }$) normal to the plane of decay was measured to be (-3.0±4.7)×${10}^{-3\mathrm{}}$ for events such that $\left({\overrightarrow{\mathrm{p}}}_{\mu }·{\overrightarrow{\mathrm{p}}}_v\right)=0\mathrm{}$. The value of $\mathrm{Im}\xi$ is then -0.016±0.025. This null result places constraints on certain models of $\mathrm{CP}$ nonconservation through the exchange of Higgs bosons.

A new, superstrong force (analogous, to, but much stronger than, quantum chromodynamics) is introduced to the Peccei-Quinn extension of the standard model of weak and electromagnetic interactions. Strong $\mathrm{CP}$ nonconservation is naturally suppressed and the resulting heavy axion is compatible with the present experimental bounds. The strength of this new force and some of its properties are discussed.

Elastic and inelastic scattering of ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ to discrete states have been measured at 695-MeV bombarding energy and the observed differential cross sections have been analyzed with a coupled-channels calculation. The obtained ion-ion potential differs significantly from those derived from previous poor-resolution experiments on similar systems, but is consistent with a global potential based upon lighter-mass systematics.

Accurate analyzing power data have been obtained for scattering of 10- and 14-MeV neutrons from ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$, with use of a new combination of techniques to produce pulsed, polarized neutron beams. Parametrization with the conventional optical model yields a spin-orbit interaction which is consistent with that observed for proton-nucleus scattering. This combined experimental and theoretical study represents the most sensitive test of similarities between proton and neutron spin-orbit potentials for medium-weight nuclei.

Ultrahigh-mass cluster ions ($\frac{m}{z}>18\mathrm{}000$) of the type ${\left[M{\mathrm{}\left(\mathrm{MX}\right)\mathrm{}}_n\right]}^{+}$ have been produced by xenon-ion bombardment of CsI and detected by a high-performance secondary-ion mass spectrometer. The mass spectra (ion intensity versus $n$) show anomalous behavior which is correlated with hypothesized dominance of cubiclike clusters having low surface energies.

The stability of ablatively accelerated single-layer and multilayer thin foil targets has been studied by x-ray shadowgraphy and x-ray spectral analysis of the rear target surface. Results show the single-layer foil acceleration to be essentially stable with the disassembly being thermally dominated. An upper limit to Rayleigh-Taylor growth of 1.8 is determined compared to a classical value of 11. Evidence, though, of internal layer mixing in the multilayer target is seen.

A modified Korteweg-de Vries equation with a cubic nonlinearity is found to describe the time evolution of propagating double layers or electrostatic shocks. The asymptotic form of the solution is discussed for a monotonic initial profile. The profile may steepen and reach a steady state simultaneously as a number of solitary waves form behind the shock, resembling the time evolution of experimentally observed shock profiles.

A new, steady-state linear mirror machine has been constructed which produces a low-density, low-temperature hydrogen plasma in the collisionality regime of the dissipative trapped-ion instability. This instability was seen and identified through the observed dependence of wave amplitude on trapped fraction, axial and radial position, and collisionality and through the scaling of real frequency with trapped fraction.

Direct numerical simulations of three-dimensional magnetohydrodynamic turbulence with kinetic and magnetic Reynolds numbers up to 100 are presented. Spatially intermittent magnetic fields are observed in a flow with nonhelical driving. Small-scale helical driving produces strong large-scale nearly force-free magnetic fields.

The $4d$ transition metal yttrium was studied at pressures up to 34 GPa by energy dispersive x-ray diffraction. The crystal-structure sequence hc${\mathrm{p}}^{\to }$Sm-${\mathrm{type}}^{\to }$double-hcp was observed with increasing pressure. This sequence is well known for the regular trivalent lanthanide metals with decreasing $4f$-electron number and under high pressure. Its observation in yttrium is conclusive experimental evidence that these structural transitions result simply from changes in $d$-band occupancy ($s\to d$ transfer) without any significant participation of $f$ electrons.

Calculations of the photoabsorption and photoyield of small metal spheres are reported for photon energies below the plasmon energy. It is found that the excitation of electron-hole pairs due to the presence of the surface results in (1) enhancements in the photo-absorption rates and photoyields that are typically 10-${10}^2$ and (2) similar enhancements in the threshold photoyields of small spheres relative to plane surfaces in agreement with recent experimental results.

The resistance of several granular NbN films has been measured as a function of temperature as they approach the superconducting state. The lowest-resistance data deviate from earlier reported power-law behavior above a phase-ordering transition $T_{cj}$, but are consistent with the exponential expression describing the resistance above a two-dimensional phase-transition temperature, $T_{2\mathrm{D}}$, of the type proposed by Kosterlitz and Thouless. At $T_{2\mathrm{D}}$ a finite supercurrent appears.

Resonance-induced enhancement of fluorescence from a thin dye layer coated on a 9.8-μm-diam glass fiber has been observed. Enhancement occurs when the wavelengths of incident radiation and/or inelastic emission are resonant with natural modes of oscillation of a circular dielectric cylinder. These dielectric resonances are comparable to surface plasmon resonances in metallic microstructures, which are partially responsible for the surface-enhanced Raman effect.

The nuclear magnetic polarization of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ on the surface of a fluorocarbon substrate is controlled by the polarization of the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ in the substrate. The apparent relaxation rates of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ measure the coupling between the spin baths of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ nuclei within the substrate.

Low-temperature infrared-saturation and hole-burning measurements have been performed on an internal vibrational mode of a spherical-top molecule embedded in a variety of alkali halide crystals. The vibrational relaxation times $T_1$ and $T_2$ satisfy the relation $T_2\cong 2T_1$ but $T_1$ (⩽ 38 nsec) is orders of magnitude smaller than expected for multiphonon decay. A study of the alkali halide dependence of these relaxation times suggests that a specific combination of internal, local, and band modes is involved in the decay process.

Spatially resolved extreme ultraviolet spectra were measured from the rear side of gold foils irradiated with 1.05-μm wavelength, 100-ps pulses at intensities of 3× ${10}^{14}$ W/${\mathrm{cm}}^2$. In the energy range of 0.1 to 1.0 keV the radiation intensity decayed exponentially with foil thickness up to 1 μm but remained almost constant over the range of 1 to 6 μm. These results indicate that radiation heat conduction plays an important role in high-$Z$ plasma energy transport. Ablation by the radiation heat flux is briefly discussed.

Use of the ASDEX divertor permits the production of stable low-density discharges ($n_e\gtrsim {10}^{12}$ ${\mathrm{cm}}^{-3\mathrm{}}$) with extremely low resistivity lasting for more than 10 s. While the distribution functions of electrons and ions show suprathermal tails, runaway electrons in the megaelectronvolt range are found to disappear with decreasing density. There are indications that in these discharges the energy confinement is improved compared with ALCATOR scaling.